Delivery of solid chemical precursors

ABSTRACT

Systems and methods are provided for delivering solid precursors in deposition processes. A flow monitor is used to measure and regulate the flow of vaporized solid precursor material from a vaporization chamber to a deposition chamber. The flow monitor chokes the supply of vapor into the deposition chamber to regulate vapor flow. To avoid condensation of the solid precursor material in the delivery lines or flow monitor, a controller is placed in a feed back loop to monitor the flow rate and make adjustments to the amount of vapor available at the inlet of the flow monitor.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of co-pending and now-allowedapplication Ser. No. 09/976,176, filed Oct. 11, 2001.

BACKGROUND OF THE INVENTION

[0002] The present invention relates in general to vapor deliverysystems for deposition processes, and in particular to systems andmethods for reliably delivering solid precursors to a depositionchamber.

[0003] Chemical vapor deposition (CVD) is a common process used in themanufacturing of films, coatings, and semiconductor devices. In a CVDprocess, a layer is formed on a substrate such as a semiconductor waferby the reaction of vapor phase chemicals on or near the surface of thesubstrate. CVD processing is highly desirable in many applications dueto it's relatively fast processing times and ability to form highlyconformal layers on irregular shaped surfaces including deep contactopenings.

[0004] CVD processes typically deliver one or more gaseous reactants tothe surface of substrates positioned within a deposition chamber undertemperature and pressure conditions favorable to the desired chemicalreactions. As such, the types of layers that can be formed on asubstrate using CVD techniques is limited by the types of reactants orprecursors that can be delivered to the surface of the substrate.

[0005] Liquid precursors are commonly used in CVD processes due to theease of their delivery to the deposition chamber. In typical liquidprecursor systems, the liquid precursor is placed in a bubbler andheated sufficiently to transform the precursor to the vapor phase. Acarrier gas typically either travels through the liquid precursor orpasses over the bubbler at a controlled rate thus saturating the carriergas with the precursor. The carrier gas then carries the liquidprecursor to the surface of the substrate. Liquid precursors arecommonly employed in CVD processes because the amount of liquidprecursor can be precisely and consistently controlled.

[0006] The techniques developed for the delivery of liquid precursorscannot be used to reliably deliver solid precursors however. It isdifficult to vaporize a solid precursor at a controlled rate such thatreproducible flows are achieved. As a solid precursor sublimates, theshape and morphology of the remaining solid precursor changes. Thechanging volume of the solid precursor results in a continuouslychanging rate of vaporization. The changing rate of vaporization isnotable particularly in thermally sensitive compounds. Additionally, anoversupply of vaporized solid precursor can result in condensation ofthe vapor back into a solid thus clogging vapor delivery lines and othermonitoring equipment. Further, the use of a carrier gas is substantiallyineffective as a means to implement rapid changes to the flow of thesolid precursors.

[0007] Despite the difficulties in delivering solid precursors in CVDprocesses, there are many desirable precursor materials including forexample, organometallic precursors, that are readily available in solidform. Further, many desirable precursor materials including organic andinorganic precursor materials may not be readily available in gas orliquid form. Also, solid precursors are particularly useful in thedeposition of metal--based films, such as metal nitrides and metalsilicides.

[0008] Therefore, there is a need in the art for a vapor delivery systemfor delivering solid precursors in a CVD process at a controllable rate.

SUMMARY OF THE INVENTION

[0009] This need is met by the present invention wherein systems andmethods are provided for delivering solid precursors in depositionprocesses. A flow monitor is used to measure the flow of vaporized solidprecursor material. The flow monitor is capable of measuring vapor flowthat is maintained at a high temperature and low inlet and outletpressure to avoid condensation of the precursor. The vapor flow measuredby the flow monitor is fed back to a controller arranged to adjust thesupply of vapor at the inlet of the flow monitor.

[0010] In accordance with one embodiment of the present invention, asolid precursor material is sublimated in a vaporization chamber byheating the solid precursor material with a fast response heater. As thevaporized solid precursor material is fed from the vaporization chamberinto a deposition chamber, a flow monitor measures the vapor flow. Thevapor flow measurements are input into a controller that communicateswith the fast response heater to effect rapid changes to the temperatureapplied to the solid precursor material. As such, the temperaturechanges affect the rate at which the solid precursor sublimates, andthus the vapor flow is controlled.

[0011] In accordance with another embodiment of the present invention, asolid precursor material is sublimated in a vaporization chamber and fedinto a deposition chamber. As the vaporized solid precursor material isfed into the deposition chamber, a flow monitor measures the vapor flow.The vapor flow measurements are input into a controller thatcommunicates with a valve positioned upstream of the flow monitor toadjust the amount of excess vapor siphoned by the valve, and thus thevapor flow is controlled.

[0012] In accordance with another embodiment of the present invention, asolid precursor material is sublimated in a vaporization chamber byheating the solid precursor material with a fast response heater. As thevaporized solid precursor material is fed from the vaporization chamberinto a deposition chamber, a flow monitor measures the vapor flow. Thevapor flow measurements are input into a controller that communicateswith the fast response heater to effect rapid changes to the temperatureapplied to the solid precursor material and/or the controllercommunicates with a valve positioned upstream of the flow monitor toadjust the amount of excess vapor siphoned by the valve, and thus thevapor flow is controlled.

[0013] Accordingly, it is an object of the present invention to providesystems and methods of delivering a solid precursor to a depositionprocess.

[0014] It is an object of the present invention to provide systems andmethods to reliably measure the vapor flow of a solid precursor.

[0015] It is an object of the present invention to provide systems andmethods to reliably and rapidly change the flow of vapor supplied to adeposition process.

[0016] Other objects of the present invention will be apparent in lightof the description of the invention embodied herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0017] The following detailed description of the preferred embodimentsof the present invention can be best understood when read in conjunctionwith the following drawings, where like structure is indicated with likereference numerals, and in which:

[0018]FIG. 1 is a schematic illustration of a vapor delivery system fora deposition process according to one embodiment of the presentinvention;

[0019]FIG. 2 is a flow chart illustrating a simplified controllerscheme;

[0020]FIG. 3 is a schematic illustration of the vapor delivery system ofFIG. 1, further illustrating multiple controller inputs and the use of apressure regulator;

[0021]FIG. 4 is a flow chart illustrating a simplified controller schemeincorporating a check to determine whether vapor is within a pressureguard band;

[0022]FIG. 5 is a schematic illustration of the vapor delivery system ofFIG. 1, further illustrating an external pressure sensor positionedalong the delivery line upstream of a flow monitor;

[0023]FIG. 6 is a schematic illustration of a vapor delivery system fordeposition processing according to another embodiment of the presentinvention;

[0024]FIG. 7 is a schematic illustration of the vapor delivery system ofFIG. 4, further illustrating the use of a pressure regulator; and,

[0025]FIG. 8 is a schematic illustration of a vapor delivery system fordeposition processing according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In the following detailed description of the preferredembodiments, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration, and not byway of limitation, specific preferred embodiments in which the inventionmay be practiced. It is to be understood that other embodiments may beutilized and that logical, mechanical and electrical changes may be madewithout departing from the spirit and scope of the present invention.

[0027] Referring to FIG. 1, a vapor delivery system 100 for thecontrolled delivery of solid precursors is illustrated. A vaporizationchamber 102 includes a housing 104 and a first surface 106 that iscoupled to a heating device 108. The heating device 108 regulates thetemperature of the first surface 106 and includes a variable temperaturecontrol 110 to adjust the temperature that the heating device 108supplies to the first surface 106. The temperature control 110 isarranged to vary the temperature of the heating device 108 over a rangeof temperatures as more fully explained herein.

[0028] During deposition processing, a solid precursor material 112 ispositioned on the first surface 106 of the vaporization chamber 102, andthe heating device 108 heats the first surface 106 to a temperaturesufficient to transform the solid precursor material 112 to a vapor 114.As such, at least a portion of the temperatures-within the range oftemperatures controllable by the temperature control 110 are sufficientto sublimate or otherwise transform the solid precursor material 112 toa vapor 114.

[0029] The heating device 108 does not need to be in direct contact withthe first surface 106. Rather, it will be understood that any couplingcan be used to transfer the energy generated by the heating device 108to heat the first surface 106. The exact relationship between theheating device 108 and the first surface 106 will depend upon suchfactors including the construction of the vaporization chamber 102, thetype of heating device 108 used, and the intended solid precursormaterial 112. For example, the heating device 108 may comprise a fastresponse heater such as a thermoelectric heater that is based upon thethermoelectric (Peltier) effect. The temperature control 110 can beimplemented as any device that adjusts the temperature output by theheating device 108. For example, the temperature control 110 maycomprise an analog switch, circuit, a PID temperature controller orother digital circuit.

[0030] As a solid precursor material 112 sublimates, the shape andmorphology of the remaining solid precursor material 112 changes. Thechanging volume of the solid precursor results in a continuouslychanging rate of vaporization. As such, the heating device 108 ispreferably capable of regulating the temperature of the first surface106 over a wide range of temperatures, room temperature to 400 degreesCelsius for example. Further, the heating device 108 should be capableof rapid temperature change. For example, a change of 20-30 degreeswithin milliseconds is preferable. The present invention is in no waylimited by the rate in which the heating device 108 can changetemperatures, however, as explained more fully herein, results ofcontrolling vapor flow may vary depending upon the ability of theheating device 108 to change temperature.

[0031] The vapor 114 travels out the vaporization chamber 102 and into adelivery line 116. The delivery line 116 comprises any tubing or conduitsuitable for routing the vapor 114. A flow monitor 118 is positionedalong the delivery line 116 in such a manner as to be able to measurethe vapor flow therethrough. As illustrated, the flow monitor 118 ispositioned inline with the delivery line 116 such that a first deliveryline section 120 routes the vapor 114 from the vaporization chamber 102to the flow monitor 118, and a second delivery line section 122 routesthe vapor 114 from the flow monitor 118 to a deposition chamber 124.

[0032] The vapor 114 flows through the deposition chamber 124 and ontoone or more substrates, wafers, or other surfaces 126. Residual vapor isdrawn from the deposition chamber 124 through the exhaust port 128 bythe pump 130. The deposition chamber 124 is also sometimes referred toas a process chamber, reactor chamber, or deposition reactor. It will beappreciated that the vapor delivery system 100 of the present inventioncan be configured to supply vaporized solid precursors to any depositionchamber 124 for material deposition performed using established CVD orany other deposition processes as are known in the art.

[0033] The flow monitor 118 comprises a device capable of accuratelymeasuring the vapor flow therethrough. The flow monitor 118 must becapable of generating accurate flow measurements at both hightemperatures and low inlet and outlet pressures with minimal andpreferably no restriction to the vapor flow. The high temperatures andlow pressures are required to maintain the solid precursor material 112in the vapor phase. As illustrated, the flow monitor 118 comprises aninlet 132, an outlet 134, a flow sensor 136, and associated electronics140. The flow monitor 118 may also optionally include therein, a flowrestrictor 138, a pressure sensor 142, a temperature sensor 144, orboth. The electronics 140 provides the ability to output the measuredflow, and optional temperature and pressure measurements. Theelectronics 140 may also perform calculations or processes required bythe flow monitor 118.

[0034] The flow monitor 118 may be implemented for example, as either ananalog or digital mass flow controller. However, a digital mass flowcontroller based upon either pulsed gate flow or sonic nozzletechnologies are preferred due to the accuracy and control afforded bysuch devices. It will be appreciated that the flow monitor 118 mayrequire additional hardware depending upon its implementation. Forexample, a thermal mass flow controller gas stick may require additionalcomponents such as pressure transducers, filters, bypass valves, and insome cases, pressure regulators (not shown). Further, some mass flowcontrollers determine vapor flow based upon a measured pressure. Assuch, one pressure sensor and the appropriate electronics can outputboth the vapor flow and pressure. Accordingly, one physical sensor ordevice can embody one or more of the sensors schematically illustratedherein.

[0035] The flow monitor 118 is capable of controlling the flow rate intothe deposition chamber 124. By controlling the flow rate into thedeposition chamber 124, the deposition rate of the solid precursormaterial 112 onto the surface of the substrate 126 positioned within thedeposition chamber 124 is controlled. The flow monitor 118 controls theflow rate of the vapor 114 into the deposition chamber 124 by chokingthe flow of vapor in the first delivery line section 120 to let thedesired amount of flow through. This is accomplished for example, byclosing the flow restrictor 138 within the flow monitor 118. However, asthe flow is choked off, the pressure upstream of the flow restrictor 138increases. Should the pressure rise too much, condensation will occur asthe vaporized solid precursor material 112 transforms back into thesolid phase. If the solid precursor material 112 transforms from thevapor phase back to the solid phase, the flow monitor 118 and firstdelivery line section 120 can clog, jam, or otherwise suffer performancedegradation.

[0036] To maintain the solid precursor material 112 in the vapor phase,a controller 146 is used to adjust the temperature of the heating device108 to account for detected or expected changes in pressure. Thecontroller 146 has a first input 148 coupled to the flow monitor 118.The first input 148 receives as an input, the vapor flow measured by theflow monitor 118. The controller 146 further includes a first output 150coupled to the temperature control 110 of the heating device 108. Thefirst output 150 is arranged to adjust the temperature generated by theheating device 108 in such a manner to control the flow of vapor 114through the vapor delivery system 100. By reducing the flow of vapor114, the pressure in the first delivery line section 120 is alsoreduced.

[0037] It will be appreciated that the controller 146 can be implementedin a number of ways. For example, the controller 146 may be implementedas dedicated hardware, as a microprocessor based circuit, as a dedicatedturnkey computer system, or a general--purpose computer running theappropriate software to implement the present invention.

[0038] Referring now to FIG. 2, a controller scheme 200 is illustrated.The measured vapor flow is read in block 202. The measured vapor flow isthen compared to a desired vapor flow in block 204. In decision block206, the measured vapor flow is tested to determine whether the measuredvapor flow is at too low a rate for the given deposition process. If themeasured flow rate is too low, the flow rate is increased in block 208,and a new measurement is taken by feeding back control to block 202. Ifthe measured flow is not too low, the measured flow is tested todetermine whether it is too high in block 210. If the measured flow istoo high, the flow rate is reduced or choked in block 212 and a newmeasurement is taken by feeding back control to block 202. Otherwise,the flow rate is acceptable, and control is fed back to block 202 totake a new measurement. It will be understood that this flow chart isonly representative of the possible implementations of the inventionmore fully described herein. Further, the desired flow may actually berepresented as a range of acceptable flows.

[0039] Referring back to FIG. 1 with reference to FIG. 2, for a givensolid precursor material 112, the controller 146 (such as a generalpurpose computer) has preprogrammed therein, a desired flow rate orrange of acceptable flow rates to achieve a desired deposition layer.When the deposition process begins, the controller 146 reads themeasured flow and compares the measured flow to the desired flow rate.If the measured vapor flow is too low, the controller 146 adjusts thetemperature of the first surface 106 of the vaporization chamber 102 bysending a control signal to the temperature control 110 of the heatingdevice 108 to affect the necessary adjustment, for example, to increasethe temperature of the first surface 106. If the measured flow exceedsthe desired flow, the output of the controller 146 signals thetemperature control 110 to reduce the temperature applied to the firstsurface 106 of the vaporization chamber 102 thus lowering the quantityof solid precursor material 112 that vaporizes and thus reduces thevapor flow. It will be appreciated that the amount of a particularadjustment will depend upon the type of solid precursor, the responsetime of the heating device 108 used, the reaction time of the flowmonitor 118 to determine the vapor flow rate, and other factors.Further, the desired flow rate may have different values during variousportions of the deposition process. The system continues to monitor thevapor flow through the flow monitor 118 and make adjustments asnecessary until the deposition process is complete.

[0040] The vapor delivery system 100 optionally includes pressureregulation to assist in maintaining the solid precursor material 112 inthe vapor phase. There are a number of ways to accomplish pressureregulation. According to one embodiment of the present invention, aninert gas is fed into the delivery line 116 as illustrated in FIG. 3.The inert gas 152 is provided by a gas source 154 and is fed into thevaporization chamber 102 through a gas line 156. A flow regulator 158 isprovided to control the amount of inert gas 152 that enters thevaporization chamber 102. The controller 146 optionally comprises asecond output 160 that couples to the flow regulator to adjust theamount of inert gas 152 that is introduced during deposition processing.

[0041] It will be observed that any number of optional flow monitors 162and valves 164 may be positioned inline with the gas line 156 beforeentering the inlet of the vaporization chamber 102. Further, whileschematically, the second output 160 of the controller 146 isillustrated as being coupled to the flow regulator 158, it will beunderstood that other control schemes may be implemented. For example,if an optional flow monitor 162, such as a digitally controlled massflow controller is positioned inline with the gas line, the secondoutput 160 of the controller 146 may couple to the mass flow controllerto regulate the amount of inert gas 152 that enters the vaporizationchamber 102 and delivery line 116.

[0042] Additionally, depending upon the selection of solid precursormaterial 112, an optional carrier gas 166 may be used to assist thevapor 114 in transmitting from the vaporization chamber 102 to thedeposition chamber 124. It will be appreciated that the carrier gas 166is supplied by the carrier gas source 167 and may utilize a second gasline 168, flow regulator 170, flow monitor 172, and other components asis known in the art. The carrier gas 166 may be fed into thevaporization chamber 102 using a second inlet (not shown), oralternatively, the carrier gas 166 may tie into the inert gas line 156downstream from the inert gas flow regulator 158.

[0043] If the flow monitor 118 includes the optional pressure sensor 142and is capable of generating an output signal representing the measuredpressure, this signal may be fed into the controller 146 as a secondinput 174. Likewise, if the flow monitor 118 includes the optionaltemperature sensor 144 and is capable of generating an output signalrepresenting the measured temperature, this signal may be fed into thecontroller 146 as a third input 176.

[0044] The addition of measured pressure and temperature data allows formore sophisticated processing by the controller 146. For example, thecontroller 146 contains predetermined data that provides the temperatureand pressure conditions required to maintain a particular solidprecursor in the vapor phase. This information may be stored forexample, in the form of a formula or lookup table. Based upon giventemperature conditions, a guard band, or range of acceptable pressuresis determined. The guard band will vary depending upon the type of solidprecursor being sublimated for deposition processing. The controller 146can now monitor both the flow rate to ensure proper depositionprocessing, and make sure the pressure is maintained within the guardband to avoid condensation from forming in the flow monitor 118 anddelivery line 116.

[0045] Referring now to FIG. 4, a controller scheme 300 includingpressure guard band testing is illustrated. The measured vapor flow isread in block 302. The measured vapor flow is then compared to a desiredvapor flow in block 304. In decision block 306, the measured vapor flowis tested to determine whether the measured vapor flow is at too low arate for the given deposition process. If the measured flow rate is toolow, the flow rate is increased in block 308, and a new measurement istaken by feeding back control to block 302. If the measured flow is nottoo low, the measured flow is tested to determine whether it is too highin block 310. If the measured flow is not too high, then control is fedback to block 302 and a new flow measurement is taken. If the measuredflow is too high, the flow rate is reduced or choked in block 312. Themeasured pressure is checked against the pressure guard band in block314 if the measured pressure is within the guard band, a new flowmeasurement is taken by feeding back control to block 302. If themeasured pressure is outside the guard band, the pressure is reduced inblock 316. It will be understood that this flow chart is onlyrepresentative of the possible implementations of the invention morefully described herein. Further, the desired flow may actually berepresented as a range of acceptable flows.

[0046] Referring back to FIG. 3, it will be appreciated that thetemperature input can also come from the heating device 108. Forexample, the heating device 108 may have a temperature output thatcouples to the third input 176 of the controller 146. Under such anarrangement, the temperature sensor 144 in the flow monitor 118 is notrequired. It will be appreciated that numerous factors affect thedecision to use a separate temperature sensor or whether the heatingdevice 108 can generate sufficient temperature measurements includingfor example, the length of the first delivery line section 120 and thetype of outputs available on the heating device 108.

[0047] The optional temperature and pressure sensors 142, 144 need notphysically reside within the flow monitor 118. Referring to FIG. 5, theflow monitor 118 does not include a built in pressure sensor. Rather, apressure sensor 178 is provided in line with the delivery line 116. Itis preferable to locate the pressure sensor 178 proximate to, andupstream from the flow monitor 118, however, the pressure sensor 178 mayalso be positioned downstream of the flow monitor 118. Further, thepressure sensor 178 may be positioned in any desired position along thedelivery line 116. It will be appreciated that a temperature sensor mayalso be positioned along the delivery line 116 (not shown) in a similarfashion as that described for the pressure sensor 178.

[0048] Referring to FIG. 6, a vapor delivery system according to anotherembodiment of the present invention is illustrated. As pointed outabove, the flow monitor 118 controls the flow rate of the vapor 114 intothe deposition chamber 124 through the second delivery line section 122by choking the flow of vapor in the first delivery line section 120 tolet the desired amount of flow through. However, as the vapor flow ischoked off, pressure upstream of the flow monitor 118 increases. Whereasan embodiment of the present invention discussed above with reference toFIGS. 1-5 offsets the increased pressure during choked off periods byadjusting the temperature of the heating device 108, the embodimentillustrated in FIG. 6 offsets the increased pressure by bleeding offexcess vapor 114.

[0049] The delivery line 116 further includes a third delivery linesection 180 that couples to the first delivery line section 120 upstreamof the flow monitor 118. A valve 182 is positioned inline with the thirddelivery line section 180, and a pump 184 is provided to draw vapor 114in the direction of the third delivery line section 180. The valve 182can be any implemented with any number of valve arrangements, includinga mass flow controller. For example, the valve 182 may comprise a pulsedgate flow or sonic nozzle mass flow controller 146. Digital valves andpulsed gate flow devices are preferred over analog counterparts due tothe fast response time and control typically afforded by such devices.

[0050] The controller 186 includes a first output 188 coupled to thevalve 182, and the logic in the controller 186 is configured to adjustthe valve 182 to selectively bleed off vapor 114 in the first deliveryline section 120 by siphoning excess vapor 114 through the thirddelivery line section 180. That is, the measured vapor flow is comparedto a predetermined vapor flow. If the measured vapor flow exceeds thedesired vapor flow, any excess vapor is bled of by opening the valve 182to draw a portion of the vapor 114 into the third delivery line section180 and away from the flow monitor 118. The controller 186 inputs andvariations thereof are similar to those described more fully herein withreference to FIGS. 1-5.

[0051] The heating device 108 is schematically illustrated as having avariable temperature control 110 because the temperature applied to thefirst surface 106 may require adjustment when switching from one solidprecursor material 112 to the next. However, in this embodiment, it isnot required that the heating device 108 be a fast response heater.

[0052]FIG. 7 illustrates the embodiment as illustrated in FIG. 6 withthe addition of optional pressure regulation to assist in maintainingthe solid precursor material 112 in the vapor phase. Similar to thepressure system discussed with reference to FIG. 3, the inert gas 152 isprovided by the gas source 154 and is fed into the vaporization chamber102 through the gas line 156. A flow regulator 158 is provided tocontrol the amount of inert gas 152 that enters the vaporization chamber102. The controller 186 optionally comprises a second output 190 thatcouples to the flow regulator 158 to adjust the amount of inert gas 152that is introduced during deposition processing. Further, depending uponthe selection of solid precursor material 112, an optional carrier gas166 may be used to assist the vapor 114 in transmitting from thevaporization chamber 102 to the deposition chamber 124. The carrier gas166 is provided by a carrier gas source 167, and is fed into thevaporization chamber 102 using a second gas line 168, flow regulator170, and other components separate from the inert gas source 154. FIG. 7also illustrates the use first, second and third controller inputs148,174, and 176 from the flow sensor 136, pressure sensor 142, andtemperature sensor 144 respectively. As previously described herein, thepressure and temperature sensors 142, 144 are optional.

[0053]FIG. 8 illustrates another embodiment of the present invention.The vapor delivery system is similar to that described with reference toFIGS. 6-7, and further includes a third output 192 that feeds backcontrol from the controller 186 to the temperature control 110 of theheating device 108. This structure allows a high degree of flexibilityin the implementation of the controller 186. For example, according toone embodiment of the present invention, the controller 186 isconfigured to adjust the temperature of the first surface 106 whencoarse adjustments are required to the vapor flow. The controller 186 isconfigured to regulate the valve 182 when fine adjustments are required.It will be appreciated that depending upon such factors as the abilityof the pump 184 to create a vacuum and the length of the third deliveryline section 180, the opening and closing the valve 182 can result infaster response times than regulating the heating device 108.

[0054] According to another embodiment of the present invention, thecontroller 186 is arranged to regulate the valve 182 and adjust thetemperature applied to the first surface 106 by adjusting thetemperature control 110 generally at the same time. Alternatively, thecontroller 186 adjusts vapor flow by adjusting the third output 192 tochange the temperature of the heating device 108, and thus affectingvapor flow, and adjusting the first and second outputs 188, 190 toadjust for measured pressure.

[0055] While illustrated having a pressure sensor 178 and a flow sensor118 that includes a built in temperature sensor 144, it will beappreciated that the inputs to the controller 186 can include any of theconfigurations discussed above with reference to FIGS. 1-7.

[0056] Although the invention described above with reference to FIGS.1-8 are illustrated with a single vaporization chamber 102 and a singlesolid precursor material 112, it will be appreciated that any number ofvaporization chambers 102 may feed into a single deposition chamber 124using the techniques, methods, and system described herein.

[0057] Further, any number of additional features of conventional vapordelivery systems may be used with the present invention as is known inthe art. For example, optional delivery line heaters may be used tomaintain the solid precursor in the vapor phase. The use of deliveryline heaters may be advantageous under conditions where excessive linelength is required to deliver the solid precursor.

[0058] Having described the invention in detail and by reference topreferred embodiments thereof, it will be apparent that modificationsand variations are possible without departing from the scope of theinvention defined in the appended claims.

What is claimed is:
 1. A vapor delivery system for a solid precursorcomprising: a vaporization chamber; a first surface within saidvaporization chamber, said first surface arranged to hold a solidprecursor material; a heating device having a temperature control, saidtemperature control arranged to vary the temperature of said heatingdevice over a range of temperatures, at least a portion of thetemperatures within said range of temperatures sufficient to transformsaid solid precursor material to a vapor, wherein said heating device isarranged to transfer heat to said first surface; a delivery line coupledto said vaporization chamber; a flow monitor arranged to measure theflow of said vapor through said delivery line; and a controller having afirst input coupled to said flow monitor and a first output coupled tosaid temperature control of said heating device, said controllerarranged to control the supply of said vapor to said delivery line byvarying said first output to adjust the temperature of said heatingdevice based at least in part on the measured flow of said vapor at saidfirst input.
 2. A vapor delivery system for a solid precursor accordingto claim 1, wherein said heating device comprises a thermoelectricheating device.
 3. A vapor delivery system for a solid precursoraccording to claim 1, wherein said heating device is arranged to heatsaid first surface to a temperature sufficient to sublimate said solidprecursor material.
 4. A vapor delivery system for a solid precursoraccording to claim 1, wherein said controller comprises a microprocessorbased controller.
 5. A vapor delivery system for a solid precursoraccording to claim 1, wherein said controller comprises a generalpurpose computer.
 6. A vapor delivery system for a solid precursoraccording to claim 1, wherein said flow monitor comprises a pulsed gateflow mass flow controller;
 7. A vapor delivery system for a solidprecursor according to claim 1, wherein said flow monitor comprises asonic nozzle mass flow controller
 8. A vapor delivery system for a solidprecursor according to claim 1, further comprising a pressure sensorarranged to measure the pressure of said vapor within said deliveryline, wherein said controller has a second input coupled to saidpressure sensor, said second input receiving as a second input signalthe measured pressure of said vapor.
 9. A vapor delivery system for asolid precursor according to claim 8, wherein said controller isarranged to vary said first output to adjust the temperature of saidheating device based at least in part on the measured pressure of saidpressure sensor.
 10. A vapor delivery system for a solid precursoraccording to claim 9, wherein said controller is arranged to comparesaid measured pressure against a guard band range of pressures, and saidcontroller varies said first output to adjust the temperature of saidheating device if said measured pressure is outside of said guard bandrange of pressures.
 11. A vapor delivery system for a solid precursoraccording to claim 1, further comprising a temperature sensor arrangedto measure the temperature of said vapor within said delivery line,wherein said controller has a second input coupled to said temperaturesensor, said second input receiving as a second input signal themeasured temperature of said vapor.
 12. A vapor delivery system for asolid precursor according to claim 1, further comprising a gas sourcecoupled to an inlet in said vaporization chamber, wherein said gassource is arranged to supply a gas to said delivery line, said gastransferred to said delivery line to regulate the pressure within saiddelivery line.
 13. A vapor delivery system for a solid precursoraccording to claim 12, wherein said controller further comprises asecond output adapted to adjust the amount of said gas that is suppliedto said delivery line by said gas source.
 14. A vapor delivery systemfor a solid precursor according to claim 12, wherein said gas comprisesan inert gas.
 15. A vapor delivery system for a solid precursorcomprising: a vaporization chamber; a first surface within saidvaporization chamber, said first surface arranged to hold a solidprecursor material; a heating device having a temperature control, saidtemperature control arranged to vary the temperature of said heatingdevice over a range of temperatures, at least a portion of thetemperatures within said range of temperatures sufficient to transformsaid solid precursor material to a vapor, wherein said heating device isarranged to transfer heat to said first surface; a delivery line coupledto said vaporization chamber; a flow monitor arranged to measure theflow of said vapor through said delivery line; a pressure sensorarranged to measure the pressure of said vapor within said deliveryline; a gas source coupled to an inlet in said vaporization chamber,said gas source arranged to supply an inert gas to said delivery line;and a controller comprising: a first input coupled to said flow monitor;a second input coupled to said pressure sensor; a first output coupledto said temperature control of said heating device, and a second outputcoupled to said gas source, wherein said controller is arranged tocontrol the supply of said vapor to said delivery line by varying saidfirst output to adjust the temperature of said heating device based atleast in part on the measured flow of said vapor at said first input,and by varying said second output to adjust the flow of said inert gasbased at least in part on the measured pressure of said vapor at saidsecond input.
 16. A vapor delivery system for a solid precursorcomprising: a vaporization chamber; a first surface within saidvaporization chamber, said first surface arranged to hold a solidprecursor material; a heating device having a temperature control, saidtemperature control arranged to vary the temperature of said heatingdevice over a range of temperatures, at least a portion of thetemperatures within said range of temperatures sufficient to transformsaid solid precursor material to a vapor, wherein said heating device isarranged to transfer heat to said first surface; a delivery line coupledto said vaporization chamber; a flow monitor arranged to measure theflow of said vapor through said delivery line; a pressure sensorarranged to measure the pressure of said vapor within said deliveryline; a temperature sensor arranged to measure the temperature of saidvapor within said delivery line; a gas source coupled to an inlet insaid vaporization chamber, said gas source arranged to supply an inertgas to said delivery line; a flow regulator coupled between said gassource and said inlet in said vaporization chamber, and a controllercomprising: a first input coupled to said flow monitor; a second inputcoupled to said pressure sensor; a third input coupled to saidtemperature sensor; a first output coupled to said temperature controlof said heating device, and second output coupled to said flowregulator, wherein said controller is arranged to control the supply ofsaid vapor to said delivery line by varying said first output to adjustthe temperature of said heating device based at least in part on themeasured flow of said vapor at said first input, and by varying saidsecond output to adjust the flow of said inert gas through said flowregulator, based at least in part on the measured pressure of said vaporat said second input, and the measured temperature of said vapor at saidthird input.
 17. A chemical vapor deposition system comprising: avaporization chamber; a first surface within said vaporization chamber,said first surface arranged to hold a solid precursor material; aheating device having a temperature control, said temperature controlarranged to vary the temperature of said heating device over a range oftemperatures, at least a portion of the temperatures within said rangeof temperatures sufficient to transform said solid precursor material toa vapor, wherein said heating device is arranged to transfer heat tosaid first surface; a deposition chamber; a delivery line arranged tocouple said vaporization chamber to said deposition chamber; a flowmonitor arranged to measure the flow of said vapor through said deliveryline; and a controller having a first input coupled to said flow monitorand a first output coupled to said temperature control of said heatingdevice, said controller arranged to control the supply of said vapor tosaid delivery line by varying said first output to adjust thetemperature of said heating device based at least in part on themeasured flow of said vapor at said first input.
 18. A vapor deliverysystem for a solid precursor comprising: a vaporization chamber; a firstsurface within said vaporization chamber, said first surface arranged tohold a solid precursor material; a heating device arranged to heat saidfirst surface sufficient to transform said solid precursor material to avapor; a delivery line coupled to said vaporization chamber, saiddelivery line arranged to route said vapor in a first direction and asecond direction; a first flow monitor arranged to measure the flow ofsaid vapor through said delivery line in said first direction; a firstvalve arranged to regulate the flow of said vapor through said deliveryline in said second direction; a first pump coupled to said deliveryline, said first pump arranged to draw vapor through said delivery linein said second direction; and a controller having a first input coupledto said first flow monitor and a first output coupled to said firstvalve, said controller arranged to bleed off excess amounts of saidvapor located in said first direction of said delivery line by varyingsaid first output to adjust said valve based at least in part on themeasured flow of said vapor at said first input.
 19. A vapor deliverysystem for a solid precursor according to claim 18, wherein saidcontroller comprises a microprocessor based controller.
 20. A vapordelivery system for a solid precursor according to claim 18, whereinsaid controller comprises a general purpose computer.
 21. A vapordelivery system for a solid precursor according to claim 18, whereinsaid first flow monitor comprises a pulsed gate flow mass flowcontroller.
 22. A vapor delivery system for a solid precursor accordingto claim 18, wherein said first flow monitor comprises a sonic nozzlemass flow controller.
 23. A vapor delivery system for a solid precursoraccording to claim 18, further comprising a pressure sensor arranged tomeasure the pressure of said vapor within said delivery line in saidfirst direction, wherein said controller has a second input coupled tosaid pressure sensor, said second input receiving as a second inputsignal the measured pressure of said vapor.
 24. A vapor delivery systemfor a solid precursor according to claim 23, wherein said controller isarranged to vary said first output to adjust said first valve based atleast in part on the measured pressure of said pressure sensor.
 25. Avapor delivery system for a solid precursor according to claim 24,wherein said controller is arranged to compare said measured pressureagainst a guard band range of pressures, and said controller varies saidfirst output to adjust said first valve if said measured pressure isoutside of said guard band range of pressures.
 26. A vapor deliverysystem for a solid precursor according to claim 18, further comprising atemperature sensor arranged to measure the temperature of said vaporwithin said delivery line in said first direction, wherein saidcontroller has a second input coupled to said temperature sensor, saidsecond input receiving as a second input signal the measured temperatureof said vapor.
 27. A vapor delivery system for a solid precursoraccording to claim 18, further comprising a gas source coupled to aninlet in said vaporization chamber, wherein said gas source is arrangedto supply a gas to said delivery line, said gas transferred to saiddelivery line to regulate the pressure within said delivery line.
 28. Avapor delivery system for a solid precursor according to claim 27,wherein said controller further comprises a second output coupled tosaid flow regulator, said second output adapted to adjust the amount ofsaid gas that is supplied to said delivery line by said gas source. 29.A vapor delivery system for a solid precursor according to claim 28,wherein said gas comprises an inert gas.
 30. A vapor delivery system fora solid precursor according to claim 18, wherein said first valvecomprises a digital valve.
 31. A vapor delivery system for a solidprecursor according to claim 18, wherein said first valve comprises apulsed gate valve.
 32. A vapor delivery system for a solid precursoraccording to claim 18, wherein said first valve is positioned upstreamof said first flow monitor.
 33. A vapor delivery system for a solidprecursor comprising: a vaporization chamber; a first surface withinsaid vaporization chamber, said first surface arranged to hold a solidprecursor material; a heating device arranged to heat said first surfacesufficient to transform said solid precursor material to a vapor; adelivery line coupled to said vaporization chamber, said delivery linearranged to route said vapor in a first direction and a seconddirection; a first flow monitor arranged to measure the flow of saidvapor through said delivery line in said first direction; a firstpressure sensor arranged to measure the pressure of said vapor withinsaid delivery line in said first direction; a first valve arranged toregulate the flow of said vapor through said delivery line in saidsecond direction; a first pump coupled to said delivery line, said firstpump arranged to draw vapor through said delivery line in said seconddirection; a gas source coupled to an inlet in said vaporizationchamber, said gas source arranged to supply an inert gas to saiddelivery line; a flow regulator between said gas source and said inletin said vaporization chamber; and a controller comprising: a first inputcoupled to said first flow monitor; a second input coupled to said firstpressure sensor; a first output coupled to said first valve; and asecond output coupled to said flow regulator; wherein said controller isarranged to bleed off excess amounts of said vapor in said firstdirection of said delivery line by varying said first output to adjustsaid valve and by varying said second output to adjust the amount ofsaid inert gas that is supplied to said delivery line by said gassource, based at least in part on the measured flow of said vapor atsaid first input and the measured pressure of said vapor at said secondinput.
 34. A vapor delivery system for a solid precursor comprising: avaporization chamber; a first surface within said vaporization chamber,said first surface arranged to hold a solid precursor material; aheating device arranged to heat said first surface sufficient totransform said solid precursor material to a vapor; a delivery linecoupled to said vaporization chamber, said delivery line arranged toroute said vapor in a first direction and a second direction; a firstflow monitor arranged to measure the flow of said vapor through saiddelivery line in said first direction; a first pressure sensor arrangedto measure the pressure of said vapor within said delivery line in saidfirst direction; a first temperature sensor arranged to measure thetemperature of said vapor within said delivery line in said firstdirection; a first valve arranged to regulate the flow of said vaporthrough said delivery line in said second direction; a first pumpcoupled to said delivery line, said first pump arranged to draw vaporthrough said delivery line in said second direction; a gas sourcecoupled to an inlet in said vaporization chamber, said gas sourcearranged to supply an inert gas to said delivery line; a flow regulatorbetween said gas source and said inlet in said vaporization chamber; anda controller comprising: a first input coupled to said first flowmonitor; a second input coupled to said first pressure sensor; a thirdinput coupled to said first temperature sensor; a first output coupledto said first valve; and a second output coupled to said flow regulator,wherein said controller is arranged to bleed off excess amounts of saidvapor in said first direction of said delivery line by varying saidfirst output to adjust said valve and by varying said second output toadjust the amount of said inert gas that is supplied to said deliveryline by said gas source, based at least in part on the measured flow ofsaid vapor at said first input, the measured pressure of said vapor atsaid second input, and the measured temperature of said vapor at saidthird input.
 35. A chemical vapor deposition system comprising: avaporization chamber; a first surface within said vaporization chamber,said first surface arranged to hold a solid precursor material; aheating device arranged to heat said first surface sufficient totransform said solid precursor material to a vapor; a depositionchamber; a delivery line arranged to couple said deposition chamber tosaid vaporization chamber, said delivery line having a first deliveryline arranged to route said vapor in a first direction from saidvaporization chamber toward said deposition chamber, and said deliveryline having a second delivery line arranged to route said vapor in asecond direction from said vaporization chamber away from saiddeposition chamber; a first flow monitor arranged to measure the flow ofsaid vapor through said delivery line in said first direction; a firstvalve arranged to regulate the flow of said vapor through said deliveryline in said second direction; a first pump coupled to said deliveryline, said first pump arranged to draw vapor through said delivery linein said second direction; and a controller having a first input coupledto said first flow monitor and a first output coupled to said firstvalve, said controller arranged to bleed off excess amounts of saidvapor in said first direction of said delivery line by varying saidfirst output to adjust said valve based at least in part on the measuredflow of said vapor at said first input.
 36. A vapor delivery system fora solid precursor comprising: a vaporization chamber; a first surfacewithin said vaporization chamber, said first surface arranged to hold asolid precursor material; a heating device having a temperature control,said temperature control arranged to vary the temperature of saidheating device over a range of temperatures, at least a portion of thetemperatures within said range of temperatures sufficient to transformsaid solid precursor material to a vapor, wherein said heating device isarranged to transfer heat to said first surface; a delivery line coupledto said vaporization chamber, said delivery line arranged to route saidvapor in a first direction and a second direction; a first flow monitorarranged to measure the flow of said vapor through said delivery line insaid first direction; a valve arranged to regulate the flow of saidvapor through said delivery line in said second direction; a first pumpcoupled to said delivery line, said first pump arranged to draw vaporthrough said delivery line in said second direction; and a controllerhaving a first input coupled to said first flow monitor, a first outputcoupled to said temperature control of said heating device, and a secondoutput coupled to said valve, said controller arranged to control thesupply of said vapor to said delivery line in said first direction basedat least in part on the measured flow of said vapor at said first inputby varying said first output to adjust the temperature of said heatingdevice and to bleed off excess amounts of said vapor in said firstdirection by varying said second output to adjust said valve.
 37. Avapor delivery system for a solid precursor according to claim 36,further comprising a pressure sensor arranged to measure the pressure ofsaid vapor within said delivery line in said first direction, whereinsaid controller has a second input coupled to said pressure sensor, saidsecond input receiving as a second input signal the measured pressure ofsaid vapor.
 38. A vapor delivery system for a solid precursor accordingto claim 37, wherein said controller is arranged to vary said firstoutput to adjust the temperature of said heating device based at leastin part on the measured pressure of said pressure sensor.
 39. A vapordelivery system for a solid precursor according to claim 38, whereinsaid controller is arranged to compare said measured pressure against aguard band range of pressures, and said controller varies said firstoutput to adjust the temperature of said heating device if said measuredpressure is outside of said guard band range of pressures.
 40. A vapordelivery system for a solid precursor according to claim 36, furthercomprising a temperature sensor arranged to measure the temperature ofsaid vapor within said delivery line in said first direction, whereinsaid controller has a second input coupled to said temperature sensor,said second input receiving as a second input signal the measuredtemperature of said vapor.
 41. A vapor delivery system for a solidprecursor according to claim 36, further comprising a gas source coupledto an inlet in said vaporization chamber, wherein said gas source isarranged to supply a gas to said delivery line, said gas transferred tosaid delivery line to regulate the pressure within said delivery line.42. A vapor delivery system for a solid precursor according to claim 41,wherein said controller further comprises a second output adapted toadjust the amount of said gas that is supplied to said delivery line bysaid gas source.
 43. A vapor delivery system for a solid precursoraccording to claim 41, wherein said gas comprises an inert gas.
 44. Avapor delivery system for a solid precursor according to claim 36,wherein said first valve comprises a digital valve.
 45. A vapor deliverysystem for a solid precursor according to claim 36, wherein said firstvalve comprises a pulsed gate valve.
 46. A vapor delivery system for asolid precursor according to claim 36, wherein said first valve ispositioned upstream of said first flow monitor.
 47. A vapor deliverysystem for a solid precursor comprising: a vaporization chamber; a firstsurface within said vaporization chamber, said first surface arranged tohold a solid precursor material; a heating device having a temperaturecontrol, said temperature control arranged to vary the temperature ofsaid heating device over a range of temperatures, at least a portion ofthe temperatures within said range of temperatures sufficient totransform said solid precursor material to a vapor, wherein said heatingdevice is arranged to transfer heat to said first surface; a deliveryline coupled to said vaporization chamber, said delivery line arrangedto route said vapor in a first direction and a second direction; a flowmonitor arranged to measure the flow of said vapor through said deliveryline in said first direction; a pressure sensor arranged to measure thepressure of said vapor within said delivery line in said firstdirection; a valve arranged to regulate the flow of said vapor throughsaid delivery line in said second direction; a first pump coupled tosaid delivery line, said first pump arranged to draw vapor through saiddelivery line in said second direction; a gas source coupled to an inletin said vaporization chamber, said gas source arranged to supply aninert gas to said delivery line; a flow regulator between said gassource and said inlet in said vaporization chamber; and a controllerhaving a first input coupled to said flow monitor, a second inputcoupled to said pressure sensor, a first output coupled to saidtemperature control of said heating device, a second output coupled tosaid valve, and a third output coupled to said flow regulator, saidcontroller arranged to control the supply of said vapor to said deliveryline in said first direction based at least in part on the measured flowand pressure of said vapor at said first and second inputs by varyingsaid first output to adjust the temperature of said heating device, tobleed off excess amounts of said vapor in said first direction byvarying said second output to adjust said valve, and by varying saidthird output to adjust the amount of inert gas in said delivery line.48. A vapor delivery system for a solid precursor comprising: avaporization chamber; a first surface within said vaporization chamber,said first surface arranged to hold a solid precursor material; aheating device having a temperature control, said temperature controlarranged to vary the temperature of said heating device over a range oftemperatures, at least a portion of the temperatures within said rangeof temperatures sufficient to transform said solid precursor material toa vapor, wherein said heating device is arranged to transfer heat tosaid first surface; a delivery line coupled to said vaporizationchamber, said delivery line arranged to route said vapor in a firstdirection and a second direction; a flow monitor arranged to measure theflow of said vapor through said delivery line in said first direction; apressure sensor arranged to measure the pressure of said vapor withinsaid delivery line in said first direction; a temperature sensorarranged to measure the temperature of said vapor within said deliveryline in said first direction; a valve arranged to regulate the flow ofsaid vapor through said delivery line in said second direction; a firstpump coupled to said delivery line, said first pump arranged to drawvapor through said delivery line in said second direction; a gas sourcecoupled to an inlet in said vaporization chamber, said gas sourcearranged to supply an inert gas to said delivery line; a flow regulatorbetween said gas source and said inlet in said vaporization chamber; anda controller having a first input coupled to said flow monitor, a secondinput coupled to said pressure sensor, a third input coupled to saidtemperature sensor, a first output coupled to said temperature controlof said heating device, a second output coupled to said valve, and athird output coupled to said flow regulator, said controller arranged tocontrol the supply of said vapor to said delivery line in said firstdirection based at least in part on the measured flow, pressure, andtemperature of said vapor at said first, second, and third inputs byvarying said first output to adjust the temperature of said heatingdevice, to bleed off excess amounts of said vapor in said firstdirection by varying said second output to adjust said valve, and byvarying said third output to adjust the amount of inert gas in saiddelivery line.
 49. A feedback system for controlling the vapor flow of asolid precursor comprising: a flow monitor arranged to measure the flowof vapor between a vaporization chamber and a deposition chamber; aheating device arranged to apply a range of temperatures to saidvaporization chamber to adjust the flow of vapor from said vaporizationchamber; and a controller arranged to adjust the temperature of saidheating device to adjust the vapor flow measured by said flow monitortoward a predetermined vapor flow.
 50. A feedback system for controllingthe vapor flow of a solid precursor according to claim 49, furthercomprising a pressure sensor arranged to measure the pressure of thevapor between said vaporization chamber and said deposition chamber,wherein said controller is arranged to adjust the pressure of the vaporby adjusting the temperature of said heating device if the measuredpressure is outside a guard band range of pressures.
 51. A feedbacksystem for controlling the vapor flow of a solid precursor comprising: aflow monitor arranged to measure the flow of vapor between avaporization chamber and a deposition chamber; a valve positionedupstream of said flow monitor; and a controller arranged to adjust saidvalve to bleed off portions of the flow of vapor to adjust the vaporflow measured by said flow monitor toward a predetermined vapor flow.52. A feedback system for controlling the vapor flow of a solidprecursor according to claim 51, further comprising a pressure sensorarranged to measure the pressure of the vapor between said vaporizationchamber and said deposition chamber, wherein said controller is arrangedto adjust the pressure of the vapor by adjusting said valve if themeasured pressure is outside a guard band range of pressures.
 53. Afeedback system for controlling the vapor flow of a solid precursorcomprising: a flow monitor arranged to measure the flow of vapor betweena vaporization chamber and a deposition chamber; a heating devicearranged to apply a range of temperatures to said vaporization chamberto adjust the flow of vapor from said vaporization chamber; a valvepositioned upstream of said flow monitor; and a controller arranged toadjust the temperature of said heating device and adjust said valve tobleed off portions of said vapor flow from said flow monitor to adjustthe vapor flow measured by said flow monitor toward a predeterminedvapor flow.
 54. A feedback system for controlling the vapor flow of asolid precursor according to claim 53, wherein said controller adjustssaid valve if the vapor flow measured by said flow monitor is greaterthan said predetermined vapor flow, and said controller adjusts thetemperature of said heating device within said range of temperatures ifthe vapor flow measured by said flow monitor is less than saidpredetermined vapor flow.
 55. A feedback system for controlling thevapor flow of a solid precursor according to claim 53, wherein saidcontroller adjusts said valve and the temperature of said heating devicesimultaneously if the vapor flow measured by said flow monitor isgreater than said predetermined vapor flow, and said controller adjuststhe temperature of said heating device if the vapor flow measured bysaid flow monitor is less than said predetermined vapor flow.
 56. Afeedback system for controlling the vapor flow of a solid precursoraccording to claim 53, wherein said controller adjusts said valve if thevapor flow measured by said flow monitor is greater than saidpredetermined vapor flow and a fine adjustment is required to adjust thevapor flow measured by said flow monitor toward said predetermined vaporflow, said controller adjusts the temperature of said heating device ifthe vapor flow measured by said flow monitor is greater than saidpredetermined vapor flow and a course adjustment is required to adjustthe vapor flow measured by said flow monitor toward said predeterminedvapor flow, and said controller adjusts the temperature of said heatingdevice if the vapor flow measured by said flow monitor is less than saidpredetermined vapor flow.
 57. A feedback system for controlling thevapor flow of a solid precursor according to claim 53, furthercomprising a pressure sensor arranged to measure the pressure of thevapor between said vaporization chamber and said deposition chamber,wherein said controller is arranged to adjust the pressure of the vaporby adjusting the temperature of the heating device if the measuredpressure is outside a guard band range of pressures.
 58. A feedbacksystem for controlling the vapor flow of a solid precursor according toclaim 53, further comprising a pressure sensor arranged to measure thepressure of the vapor between said vaporization chamber and saiddeposition chamber, wherein said controller is arranged to adjust thepressure of the vapor by adjusting said valve if the measured pressureis outside a guard band range of pressures.